Filter GridView with multiple CheckBoxList in ASP.Net

hello good evening all of you

i saw you link (http://www.aspforums.net/Threads/155013/Filter-ASPNet-GridView-data-based-on-CheckBoxList-Checked-Items/), that is great , so i have one query .

How to filter gridview with 4 checkboxlists for Product search

CheckboxList2 -DISCOUNT   CheckboxList3 - Price   CheckboxList4 - BRAND   CheckboxList5 - Category 

but one think is that without removing any checked data on checkboxlist when select any checkboxlist item. like snapdeal,flipkart etc ,please help me anyone .